Is this eta visa is necessary to Indians to work in Canada ... Or in any other way Indians can work in Canada . .We don't have any Green Card ... How can i get eta visa.. Can i?
An ETA is not a visa but a permit for a visa exempt passport holder to allow them to board a plane. Indian passport holders cannot apply for an ETA as they are not visa exempt for Canada.
To work in Canada you would need to find an employer to sponsor an LMIA with a job offer which generally is almost impossible from outside Canada. Note there are many agents around who make false promises of a job, take your money, but in the end there is no job.
A green card has nothing to do with Canada as that is a US process.
Your post title is confusing, do you already have somebody promising you a job ?